Plastic doors for automobiles have been used and are desirable because of their light weight. While it would be desirable to make doors completely out of plastic, this is impractical because the upper door frame including the window area would lack sufficient ridigity. Therefore, the door frame including the window must generally be made of high strength material, such as steel or other metal.
When the door frame is made of metal, such as steel, the problem of attaching the door frame to the rest of the plastic door arises. The attachment problem is compounded by the fact that a door side intrusion beam must also be provided for protection against side impacts.